Sami Al Sanea - State of the Art in the Use of Thermal Insulation in Building Walls and Roofs part 2

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  • 1. PRESENTATIONState of the Art in the Use of ThermalInsulation in Building Walls and Roofs – Part II By Prof. Sami Ali Al-Sanea Department of Mechanical Engineering, King Saud University, Riyadh, KSA Copyright - Al-Sanea; KSU; Jan 2012 1
  • 2. Objectives• Outline importance of thermal insulation.• Highlight proper use of thermal insulation.• Warning against presence of thermal bridges.• Introducing concept of smart walls.• Introducing concept of critical mass. Copyright - Al-Sanea; KSU; Jan 2012 2
  • 3. Contents• Introduction; electric energy consumption.• Present status.• Is there a “best” insulation material to use?• Insulated Hordi (rib-slab) roofs.• Thermal bridges in insulated walls.• Insulation and “smart walls”.• Insulation and “critical” thermal mass. Copyright - Al-Sanea; KSU; Jan 2012 3
  • 4. Introduction (1/6): Electric energy consumption Estimate of electric energy consumption in KSA: Residential Commercial Agricultural industrial ≈ 2/3 of electric energy generated in KSA is used in buildings. Copyright - Al-Sanea; KSU; Jan 2012 4
  • 5. Introduction (2/6): Electric energy consumption Estimate of electric energy consumption in KSA: Generated Consumed in Consumed Consumed by buildings by AC transmission 100% ≈ 2/3 ≈ 2/3 ≈ 2/3 of gen. of builds. of AC • 2/3 × 2/3 × 2/3 ≈ 30%. • Hence, ≈ 30% of total electric energy generated is consumed by transmission loads in walls/roofs. • Insulation is effective means of energy savings. Copyright - Al-Sanea; KSU; Jan 2012 5
  • 6. Introduction (3/6): How much electric energy can be saved by using insulation?Compared to un-insulated wall (R ≈ 0.4 m2.K/W),insulated wall (R ≈ 2.0 m2.K/W) saves: Transmission AC Building Generated ≈ 80% ≈ 55% ≈ 35% ≈ 25% • Applying insulation is, therefore, a must. • More savings achieved under opt. condts. Copyright - Al-Sanea; KSU; Jan 2012 6
  • 7. Introduction (4/6): AC consumption constitutes big portion of total electric energy use in GCC region• Extreme temperature in summer.• Buildings not designed to conserve energy.• Improper settings of thermostat.• Thermal bridging effects.• Subsidized electric energy cost.• Awareness and habit of consumers. Copyright - Al-Sanea; KSU; Jan 2012 7
  • 8. Introduction (5/6): Increasing demand on electricity• Increasing population.• Expansion / development plans.• Increasing demand on thermal comfort. Copyright - Al-Sanea; KSU; Jan 2012 8
  • 9. Introduction (6/6): Present and future problems • Cost of energy is increasing worldwide. • Insufficient supply of electricity, especially at peak hours. • Adverse impact on environment by energy production plants. • Increasing demand on electricity. Copyright - Al-Sanea; KSU; Jan 2012 9
  • 10. Present Status (1/5): General• Increasing use of insulation without proper scientific guidance.• Building Codes are based on Int. Standards.• Recommended R-values need to be established rigorously under local condts.• Scientific research must be encouraged and be generously funded. Copyright - Al-Sanea; KSU; Jan 2012 10
  • 11. Present Status (2/5): Requirements Insulation Climatic Wall/Roof Numerical Properties Conditions Configuration Input Thermal Analysis Thermal Characteristics & Yearly Transmission Loads Economic Economic Analysis ParametersOptimum Insulation Thickness & Recommended R-Value Copyright - Al-Sanea; KSU; Jan 2012 11
  • 12. Present Status (3/5): Active research areas (I)• Proper location of insulation and thermal mass layers in building envelope. Effect of AC operation mode (continuous/intermit.).• Splitting insulation into two/three layers.• Optimization of insulation layer thickness.• Use of critical amount of thermal mass. Copyright - Al-Sanea; KSU; Jan 2012 12
  • 13. Present Status (4/5): Active research areas (II)• Thermostat settings for maximum energy savings while maintaining thermal comfort.• Effects of thermal bridges on transmission loads and opt. insulation thickness (Lopt).• Effects of economic parameters on Lopt.• Effect of wall orientation on Lopt. Copyright - Al-Sanea; KSU; Jan 2012 13
  • 14. Present Status (5/5): Active research areas (III) • Develop new building and insulation materials. • Use of phase change materials (pcm) in building envelope. • Use of roof garden and roof pond cooling. • Etc. Copyright - Al-Sanea; KSU; Jan 2012 14
  • 15. Representative Insulation Materials (1/7) Molded Polystyrene Copyright - Al-Sanea; KSU; Jan 2012 15
  • 16. Representative Insulation Materials (2/7) Extruded Polystyrene Copyright - Al-Sanea; KSU; Jan 2012 16
  • 17. Representative Insulation Materials (3/7) Polyurethane Copyright - Al-Sanea; KSU; Jan 2012 17
  • 18. Representative Insulation Materials (4/7) Glass Fiber Copyright - Al-Sanea; KSU; Jan 2012 18
  • 19. Representative Insulation Materials (5/7) Rock Wool Copyright - Al-Sanea; KSU; Jan 2012 19
  • 20. Representative Insulation Materials (6/7) Perlite Copyright - Al-Sanea; KSU; Jan 2012 20
  • 21. Representative Insulation Materials (7/7) Lightweight Concrete Copyright - Al-Sanea; KSU; Jan 2012 21
  • 22. Topic 1: “Best” insulation to use (1/3)• Insulation materials differ with respect to properties and cost.• Properties include thermal, mechanical, etc. characteristics of materials.• Cost constantly changes with time.• Insulation should be looked upon as system.• Insulation is used according to application. Copyright - Al-Sanea; KSU; Jan 2012 22
  • 23. Topic 1: “Best” insulation to use (2/3) Therefore:• There is no such material as the best insulation material.• Type of application, climate, cost, thermal properties and other properties determine what insulation material to use.• This explains presence of various types of insulations in market. Copyright - Al-Sanea; KSU; Jan 2012 23
  • 24. Topic 1: “Best” insulation to use (3/3)Example: Molded Polystyrene Extruded PolystyreneCheaper (per unit mass) More expensiveLarger k (for same ρ, temp., Smaller kand moisture content)Higher moisture absorptivity Lower moisture(adversely affecting k) absorptivity• Therefore, to select an insulation, a compromisewould often be made according to application. Copyright - Al-Sanea; KSU; Jan 2012 24
  • 25. Topic 2: Hordi (rib-slab) roofs (1/11) Hordi roof versus solid-slab roof Outside 20 Tiles 30 Mortar bed Lins Insulation Membrane 5 75 Foam concrete 130 or Reinforced concrete 200 25 Cement plaster Inside Copyright - Al-Sanea; KSU; Jan 2012 25
  • 26. Topic 2: Hordi roofs (2/11) Copyright - Al-Sanea; KSU; Jan 2012 26
  • 27. Topic 2: Hordi roofs (3/11) Hordi roof versus solid-slab roof• Increasing use of Hordi roofs due to advantages over solid-slab roofs.• R-values of Hordi roofs are often larger than R-values of solid-slab roofs.• When Hordi units are made of insulating materials, the roofs become lighter and offer further increase in R-value and sound proof. Copyright - Al-Sanea; KSU; Jan 2012 27
  • 28. Topic 2: Hordi roofs (4/11) Recent advances in Hordi roof design• Hordi roofs, with insulating Hordi units, suffer from effects of thermal bridges.• Novel and practical Hordi roof design that eliminates thermal bridges was sought.  With the new design, substantial energy savings can be achieved.  Hot and cold spots are eliminated resulting into better thermal comfort. Copyright - Al-Sanea; KSU; Jan 2012 28
  • 29. Topic 2: Hordi roofs (5/11) Recent advances in Hordi roof design• The following results are extracted from the reference below, in which the improved Hordi unit design is the idea of the authors and should not be used without their consent. Al-Sanea S.A. and Zedan M.F., "Preventing Thermal Bridging Effects in Hordi Roofs by Using a Novel Design for the Hordi Unit", Proceedings of the Seventh Saudi Engineering Conference, Volume I, pp. 237-257, KSU, Riyadh, 2-5 Dec. 2007. Copyright - Al-Sanea; KSU; Jan 2012 29
  • 30. Topic 2: Hordi roofs (6/11) Recent advances in Hordi roof design Reinforced Reinforced concrete concrete Hordi unit Hordi unit Air Air space Rib space Rib Inside plaster Inside plaster “Not to scale”Figure 1: Conventional Hordi unit. Figure 2: Improved Hordi unit. Copyright - Al-Sanea; KSU; Jan 2012 30
  • 31. Topic 2: Hordi roofs (7/11) Recent advances in Hordi roof designInside-surface temperature versus Transmission load versus timeroof width. of day. Copyright - Al-Sanea; KSU; Jan 2012 31
  • 32. Topic 2: Hordi roofs (8/11) Recent advances in Hordi roof designDaily-total transmission load for Peak transmission load forrepresentative day of each month. representative day of each month. Copyright - Al-Sanea; KSU; Jan 2012 32
  • 33. Topic 2: Hordi roofs (9/11)• Recent advances in Hordi roof design.• Temperature contours.Copyright - Al-Sanea; KSU; Jan 2012 33
  • 34. Topic 2: Hordi roofs (10/11) • Recent advances in Hordi roof design. • Overall thermal characteristics. Transmission load Roof R-value Time Decrement Peak load (kWh/m2.yr) (m2.K/W) Lag factor (W/m2) (tlag) (df)Hordi unit Cooling Heating Dynamic Nominal (h) (%) Cool Heat (Qi,cool) (Qi,heat) (Rd) (Rn) (qpeak,c) (qpeak,h)Conventional 17.08 6.46 2.04 1.79 13.7 0.35 5.07 3.70Improved 11.09 4.12 3.16 2.92 13.0 0.15 3.23 2.30Difference 35% 36% 35% 39% 57% 36% 38% Copyright - Al-Sanea; KSU; Jan 2012 34
  • 35. Topic 2: Hordi roofs (11/11)• Recent advances in Hordi roof design.• Overall thermal bridging effects. Transmission load (kWh/m2.yr) Qrib/tot Arearib/tot Ibr (%) (%) (-)Hordi unit Rib Hordi Total (Qi,rib) (Qi,Hordi) (Qi,tot)Conventional 9.83 13.71 23.54 41.8 20 5.5Improved 3.44 11.77 15.21 22.6 20 1.3Difference 65% 14% 35% Copyright - Al-Sanea; KSU; Jan 2012 35
  • 36. Topic 3: Thermal bridges in insulated walls (1/12) Hmj Mortar joint Overall vertical Masonry section in wall H Hb showing whole Insulation building-block units and mortar joints Masonry cutting across with air space insulation layer. Outside Inside Copyright - Al-Sanea; KSU; Jan 2012 36
  • 37. Topic 3: Thermal bridges in insulated walls (2/12) Outside Inside Mortar joint Hmj/2 Cement plaster Cement plaster Insulation Air space Hb/2 Concrete Concrete Concrete H y x 25 45 75 30 25 25 25 L Symmetric region showing various layers (dimensions in mm). Copyright - Al-Sanea; KSU; Jan 2012 37
  • 38. Topic 3: Thermal bridges in insulated walls (3/12) Common and Serious Problem • Almost all insulated building blocks suffer from thermal bridges (as manufactured and/or due to adding mortar joints at construction site). • Such walls have R-values that are rather low (less than 1 m2.K/W) which are well below “recommended” R-values. Copyright - Al-Sanea; KSU; Jan 2012 38
  • 39. Topic 3: Thermal bridges in insulated walls (4/12) Common and Serious Problem • The following results are extracted from the reference below, which is presently submitted for publication. Sami A. Al-Sanea and M. F. Zedan, “Effect of Thermal Bridges on Transmission Loads and Thermal Resistance of Building Walls under Dynamic Conditions”, paper submitted for publication, 2012. Copyright - Al-Sanea; KSU; Jan 2012 39
  • 40. Topic 3: Thermal bridges in walls (5/12)Transmission load variation with time during representative daysof August and January for different mortar joint heights. Copyright - Al-Sanea; KSU; Jan 2012 40
  • 41. Topic 3: Thermal bridges in walls (6/12)(a) (b)Cool. and heat. transmission loads for representative days of monthsfor different mortar joint heights; (a) daily loads and (b) peak loads. Copyright - Al-Sanea; KSU; Jan 2012 41
  • 42. Topic 3: Thermal bridges in walls (7/12)(a) (b)Cooling and heating transmission loads variation with mortar jointheight; (a) yearly loads and (b) peak loads. Copyright - Al-Sanea; KSU; Jan 2012 42
  • 43. Topic 3: Thermal bridges in walls (8/12)Variation of dynamic and nominal thermal resistances withmortar joint height. Copyright - Al-Sanea; KSU; Jan 2012 43
  • 44. Topic 3: Thermal bridges in walls (9/12)(a) (b)Variation of thermal characteristics with mortar joint heights; (a)yearly-averaged time lag and (b) yearly-averaged decrement factor. Copyright - Al-Sanea; KSU; Jan 2012 44
  • 45. Topic 3: Thermal bridges in walls (10/12)(a) (b)Percentage change versus percentage mortar joint area to total wallarea; (a) increase in yearly cooling transmission loads and (b)decrease in yearly-averaged dynamic thermal resistance. Copyright - Al-Sanea; KSU; Jan 2012 45
  • 46. Topic 3: Thermal bridges in walls (11/12) Possible solutions• Using “insulating” mortar joint material. This can help but does not necessarily eliminate problem. Also, possible weakness regarding structural strength.• Using tongue-and-groove type of insulation. However, problems can arise with regard to stacking and storage and structural strength. Copyright - Al-Sanea; KSU; Jan 2012 46
  • 47. Topic 3: Thermal bridges in walls (12/12)Possible solution: Tongue-and-groove arrangement. Copyright - Al-Sanea; KSU; Jan 2012 47
  • 48. Topic 4:Insulation andsmart walls(1/13)All insulatedwalls have sameoptimal R-value of2.75 m2.K/W andsame thermalmass. Copyright - Al-Sanea; KSU; Jan 2012 48
  • 49. Topic 4: Insulation and smart walls (2/13)• How can thermal insulation and thermal mass complement each other in building envelope?• Introducing concept of smart wall.• Novel and practical wall design that achieves best overall dynamic thermal characteristics was sought. Copyright - Al-Sanea; KSU; Jan 2012 49
  • 50. Topic 4: Insulation and smart walls (3/13) Recent advances in wall design• Novel and practical wall design achieves:  substantial reduction in total and peak transmission loads,  substantial increase in time lag (shift in peak load) and hence makes electric-grid load profile more evenly distributed, and  substantial decrease in decrement factor. Copyright - Al-Sanea; KSU; Jan 2012 50
  • 51. Topic 4: Insulation and smart walls (4/13) Representation of time lag and decrement factor: Ai Ts ,i ,max  Ts ,i ,mintlag = tTs,o,max - tTs,i,max df   Ao Ts ,o,max  Ts ,o,min tlag Wall Ts,o,max Ts,i,max Ts,o(t) Ao Ai t Ts,i(t) Ts,i,min Inside Outside Ts,o,min x=0 x=L tTs,i,max tTs,o,max Copyright - Al-Sanea; KSU; Jan 2012 51
  • 52. Topic 4: Insulation and smart walls (5/13)• The following results are extracted from the reference below, which has been published recently in Applied Energy. Al-Sanea, S.A., Zedan, M.F., Improving thermal performance of building walls by optimizing insulation layer distribution and thickness for same thermal mass, Applied Energy 88 (2011) 3113-3124. Copyright - Al-Sanea; KSU; Jan 2012 52
  • 53. Topic 4: Insulation and smart walls (6/13) Monthly settings of indoor air temperature, Tf,i (oC).Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov DecTf,i 21 21 21 24 26 26 26 26 26 24 21 21 Values of parameters used in economic model. ci cad ce pc pf m rd ri ($/m3) ($/m2) ($/kWh) (years) (%) (%) 42.67 * 0.0317 3 4 30 5 3 Copyright - Al-Sanea; KSU; Jan 2012 53
  • 54. Topic 4: Insulation and smart walls (7/13) Material properties. Material k (W/m.K)  (kg/m3) c (J/kg.K)HWHCB* (100 mm) 0.81 1618 840Cement plaster 0.72 1860 840Molded polystyrene 0.034 23 1280 * Values of properties quoted correspond to block thickness of 100 mm. Properties of hollow masonry blocks can depend on block thickness due to different void configurations. Copyright - Al-Sanea; KSU; Jan 2012 54
  • 55. Topic 4: Insulation and smart walls (8/13)Time lag for representative days of months for various walls. Copyright - Al-Sanea; KSU; Jan 2012 55
  • 56. Topic 4: Insulation and smart walls (9/13)Decrement factor for representative days of months for various walls. Copyright - Al-Sanea; KSU; Jan 2012 56
  • 57. Topic 4: Insulation and smart walls (10/13)Peak cool. Transm. loads for representative days of months for walls. Copyright - Al-Sanea; KSU; Jan 2012 57
  • 58. Topic 4: Insulation and smart walls (11/13)Transm. load versus time during represent. day of Aug. for walls. Copyright - Al-Sanea; KSU; Jan 2012 58
  • 59. Topic 4: Insulation and smart walls (12/13)Temperature distribution across wall thickness at different timesduring representative day of August for wall W3. Copyright - Al-Sanea; KSU; Jan 2012 59
  • 60. Topic 4: Insulation and smart walls (13/13)Yearly transmission loads, yearly-averaged time lag and decrement factor, andpeak transmission loads for different walls with optimized insulation thickness. Transmission load Time lag Decrement Peak loads* (kWh/m2.yr) (tlag) factor (W/m2)Wall Cooling Heating (h) (df) Cool Heat (Qi,cool) (Qi,heat) (%) (qp,cool) (qp,heat)W1a 13.18 5.041 6.13 1.35 4.77 3.36W1b 13.19 5.061 7.33 1.34 4.79 3.42W1c 13.03 4.957 6.71 0.74 4.41 3.15W2a 13.00 4.870 9.33 0.42 4.02 2.86W2b 12.97 4.889 8.19 0.24 3.91 2.78W2c 12.96 4.889 10.44 0.26 3.92 2.80W3 12.97 4.887 12.13 0.13 3.80 2.69* Peak cooling and heating transmission loads occur in August and January for all walls. Copyright - Al-Sanea; KSU; Jan 2012 60
  • 61. Topic 5: Insulation and critical mass (1/12) Inside OutsideCement plaster (1.5 cm) Cement plaster (1.5 cm) Thermal mass; Thermal Insulation (9 cm) varying thicknessWall configurations with varying thermal mass thickness butsame and constant Rn-value; wall W1 with outside insulationand wall W2 with inside insulation. Copyright - Al-Sanea; KSU; Jan 2012 61
  • 62. Topic 5: Insulation and critical mass (2/12)Motivation• Can transmission load be reduced, and hence energy be saved, by thermal mass alone, while keeping wall R-value constant?• Walls in „moderate‟ climates are built massive!• What is the „critical‟ thickness of thermal mass and how much energy, if any, can be saved?• We do have „moderate‟ months in GCC region, can we utilize thermal mass for energy savings? Copyright - Al-Sanea; KSU; Jan 2012 62
  • 63. Topic 5: Insulation and critical mass (3/12)• The following results are extracted from the reference below, which has been published very recently in Applied Energy. Al-Sanea, S.A., Zedan, M.F., and Al-Hussain, S.N., Effect of thermal mass on performance of insulated building walls and the concept of energy savings potential, Applied Energy 89 (2012) 430-442. Copyright - Al-Sanea; KSU; Jan 2012 63
  • 64. Topic 5: Insulation and critical mass (4/12) 2 W1, cool. W2, cool. W1, heat. W2, heat. 1 Qi (kWh/m2.day) × 100 0 0 -1 -2 -3 0 0.1 0.2 0.3 0.4 0.5 Lmas (m)Daily cooling and heating transmission loads variation withmasonry thickness in November for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 64
  • 65. Topic 5: Insulation and critical mass (5/12) 10 W1, cool. W2, cool. 9 Qi,c (kWh/m2.day) × 1000 8 7 6 5 0 0.1 0.2 0.3 0.4 0.5 Lmas (m)Daily cooling transmission load variation with masonrythickness in August for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 65
  • 66. Topic 5: Insulation and critical mass (6/12) 15 W1, cool. W2, cool. 14.5 Qi,c (kWh/m2.yr) d 14 13.5 13 12.5 12 0 0.1 0.2 0.3 0.4 0.5 Lmas (m)Yearly cool. Transm. loads variation with masonry thickness forwalls W1 and W2; asymptotes and Lmas,cr by using 5% criterion. Copyright - Al-Sanea; KSU; Jan 2012 66
  • 67. Topic 5: Insulation and critical mass (7/12) 10 W1, cool. W2, cool. 8 W1, heat. W2, heat. 6 4 qpeak (W/m2) 2 0 -2 -4 -6 0 0.1 0.2 0.3 0.4 0.5 Lmas (m)Yearly peak cooling and heating transmission loads variationwith masonry thickness for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 67
  • 68. Topic 5: Insulation and critical mass (8/12) W1 W2 14 12 tlag (h) 10 8 6 4 2 0 0 0.1 0.2 0.3 0.4 0.5 Lmas (m) Yearly-averaged time lag variation with masonry thickness for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 68
  • 69. Topic 5: Insulation and critical mass (9/12) 4 W1 W2 3 df ×100 2 1 0 0 0.1 0.2 0.3 0.4 0.5 Lmas (m) Yearly-averaged decrement factor variation with masonry thickness for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 69
  • 70. Topic 5: Insulation and critical mass (10/12) 3.5 R (m2.K/W) 3 2.5 W1, dyn. R W1, nom. R W2, dyn. R W2, nom. R 2 0 0.1 0.2 0.3 0.4 0.5 Lmas (m)Yearly-averaged dynamic and nominal R-values variationwith masonry thickness for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 70
  • 71. Topic 5: Insulation and critical mass (11/12) 35 W1, cool. W1, heat. W2, cool. W2, heat. 30 25 Lmas,cr (cm) 20 15 10 5 0 70 75 80 85 90 95 100 Energy savings potential, Δ (%)Critical thermal mass thickness variation with cooling andheating energy-savings potentials for walls W1 and W2. Copyright - Al-Sanea; KSU; Jan 2012 71
  • 72. Topic 5: Insulation and critical mass (12/12) 45 Aug. Jan. 40 Nov. 35 T (oC) 30 25 20 15 10 5 0 6 12 18 24 Time (h) Outdoor air temp. variation with time of day in Aug., Jan., and Nov. showing thermostat settings of indoor air temp. Copyright - Al-Sanea; KSU; Jan 2012 72
  • 73. Conclusions (1/2)• “Best” insulation to use depends on many factors including type of application.• Thermal bridges in Hordi (rib-slab) roofs should be eliminated.• Thermal bridges in insulated walls should be eliminated.• Concept of “smart walls” should be utilized. Copyright - Al-Sanea; KSU; Jan 2012 73
  • 74. Conclusions (2/2)• Concept of “critical” thermal mass should be utilized.• Recommended R-values for building walls and roofs must be determined and/or be revised based on local conditions.• Scientific research in thermal insulation use must be encouraged. Copyright - Al-Sanea; KSU; Jan 2012 74
  • 75. THANK YOUCopyright - Al-Sanea; KSU; Jan 2012 75